The present inventions relate to an apparatus and methods for washing a borehole in a subterranean wells and for expansion of a radially expandable sand-control screen in the borehole.
The control of the movement of sand and gravel into a wellbore has been the subject of much importance in the oil production industry. The introduction of sand materials into the well commonly causes problems including, plugged formations or well tubings, and erosion of tubing and equipment. There have therefore been numerous attempts to prevent the introduction of sand and gravel into the production stream. One sand control method includes the placement of a radially expandable screen assembly in the borehole.
Another problem in the art is the flow resistance often encountered at the wall of the hole, commonly referred to as the xe2x80x9cskin factorxe2x80x9d. The skin factor at the wall of the wellbore must often be reduced before a sand-control screen assembly is installed in the formation. It is known in the art to reduce skin factor by washing the wellbore with a fluid chosen for well and formation conditions. Washing procedures also function to flush loose sand, cuttings and other debris from the borehole. The washing is performed in a trip downhole separate from the one or more trips needed for installing and expanding the screen jacket assembly. Each trip downhole requires additional time and expense.
Due to the aforementioned problems, a need exists for improved apparatus and methods for reducing skin factor in a wellbore and expanding a radially expandable sand-control screen jacket assembly in the well.
The present invention relates to an apparatus and method for washing a subterranean well borehole and radially expanding a screen assembly therein. The apparatus comprises a radially expandable screen assembly, a washing assembly adjacent the screen assembly for washing the borehole annular space, and an expansion assembly for radially expanding the screen assembly. The washing assembly can include a washing assembly housing having a wall defining an interior passage, a wash port through the housing wall for providing fluid communication between the interior passage of the washing assembly and the borehole annular space, and a flow control element affixed to the washing assembly housing for substantially preventing fluid flow along the screen annular space. The apparatus can include a force generator, preferably hydraulically powered by the washing fluid, for operating the expansion assembly. The expansion assembly can include a radially expandable swedge. The method of expanding the screen may be in the downhole or uphole direction.
The apparatus can further comprise a return flow passage providing fluid communication between an area of the borehole downhole from the expansion assembly to an area of the borehole uphole from the expansion assembly. The return flow passage can include closeable return ports, and a relief valve.